1. Field of the Invention
The present invention relates to a piston and more particularly to a piston assembly for an internal combustion engine having a fusible core to form a cooling channel and a method for the manufacture thereof.
2. Background of the Related Art
A conventional method for manufacturing a piston is disclosed in Japanese Unexamined Publication No. 51(1976)-99719, and is shown in FIG. 5. First, a piston 70 is formed by casting (e.g., by gravity die casting or squeeze casting, etc.). The piston 70 is a unitary casting defining a piston crown portion 71, combustion chamber portion 72, a piston skirt portion 73 surrounding a cavity 74, and a pair of bosses 75. Grooves 76 are then cut in a peripheral surface of the piston crown portion 71 and a pair of holes 77 are formed in the bosses 75.
Next, a ring shaped groove 78 is cut in the piston crown portion 71. An inlet 79 and an outlet 80 are cut in the piston for connecting between the cavity 74 and the ring shaped groove 78. A ring member 81 is put into an upper portion of the ring shaped groove 78, and the ring member 81 is welded to the piston 70 by friction welding.
Therefore, the piston 70 has a cooling channel system 84. When the piston 70 is driven in an engine (not shown), oil pumped out from a pump 83 through a nozzle 82 enters the ring shaped groove 78 through the inlet 79. The oil in the ring shaped groove 78 cools the piston crown portion 71 and is discharged back to the cavity 74 through the outlet 80. Consequently, the piston 70 is cooled so that its life is long.
In the above-described method for manufacturing the piston, the cooling chanel system 84 is formed in the piston by use of welding processes and cutting processes, which are time consuming.